Electron beam measuring technology is currently used for error analysis and voltage measurement in integrated circuits. However, in modern circuits this technology comes up against certain limits which can only be overcome with difficulty.
For instance, modern circuits frequently include multi-layer wiring, so that some of the measurement points in question are not accessible to the electron beam.
Furthermore, circuits are coated with an insulating passivation layer which must be removed before measurement since it is only possible to carry out qualitative, not quantitative measurements through the passivation layer.
Because of the necessary low electron energy of the scanning electron beam, electrical and magnetic fields produced by the testpiece also have a disruptive effect. These fields deflect the primary electron beam so that it is difficult to keep it on the conductive track under examination.
In order to solve the first two problems mentioned above, ion beam devices are known by means of which holes are etched through upper metal planes or through passivation layers in order to expose the measurement point in question. An ion beam device of this type is described for example in "Proceedings of the Intern, Reliability Physics Symposion", 1989, pages 34-52.
However, according to the etching process a separate electron beam tester is necessary for the actual potential measurement. Thus two separate devices are necessary, which is not only costly by also very time-consuming since the point in question has to be found again every time. There is also the difficulty that the testpiece has to be reintroduced into the ion beam device whenever a new measurement point is required which has not been previously prepared.
In order to solve the third problem mentioned in the introduction (deflection of the electron beam by disruptive influences) it was necessary in the past to use costly electronic compensation methods.